Terraria DxD: Lunatics
by Tehpootisman
Summary: The Moon Lord, Lunaris, finds himself in the world of Highschool DxD, along with his overly-affectionate Lunatic Cultist and his lovable idiot "son", Sensou the Cyborg. His brother's here too somewhere, and he must help him out by pulling some strings behind the scenes, both physically, metaphysically, and metaphorically. Companion story to Terraria DxD: Great King Cthulhu.


**Ayyy welcome to this really amazing sidestory wow!**

 **Warning: Heavy spoilers ahead if you haven't already watched the anime or read the light novel/manga. (Is there a manga? I dunno.)**

 **Also there's heavy spoilers for some of my other works literally right below this pre-chapter author's note, so yeah. It's mostly spoilers for my webcomic, Going Lunar.**

 **But hey, alternate universes are weird!**

 **This story ties in with Great King Cthulhu, alrighty? It's gonna take place after chapter 6, after it's uploaded!**

 **Toodles!**

 **oh yeah btw this one's a _little_ more OP than Cthulhu.**

* * *

 _He held the gun to his chin, fully loaded with Explosive Bullets._

 _He had been the reason why his brother died! It was all his fault! He had gone after the mothership!_

 _He didn't actually expect him to take on the mothership, let alone there being a mothership in the first place!_

 _He had summoned the Martians so that he could be the hero!_

 _In a moment of disillusionment, he felt somewhat abandoned, prompting him to do what he did._

 _Not only had the mothership appeared, but they had actually kidnapped him and took him to a minor ship nobody would think about checking for prisoners!_

 _He couldn't take it anymore as tears streamed down his face. His hands trembling, he pulled the trigger._

* * *

 _Light flooded his eyes as he found himself in a whole new environment, his cybernetics booting up and going through diagnostics._

 _Airless, cold, and silent._

 _Was this...the moon?_

 _Touching his face, he could feel dried blood, but no bullet wound._

 _Well, of course there'd be no wound, there'd be no head left considering the ammo he used._

 _Turning around, he saw something familiar from the photographs recovered from old human facilities._

 _Earth. The planet of the humans._

 _He felt a familiar presence. It was simply a pinprick of energy from here, but he could feel it down on Earth._

 _He smiled._

 _He could finally rejoin his brother._

 _Before he could take off, however, he felt a hand on his shoulder._

 _There she was. His overly obsessed lover, the one who would always sneak into his bed at night._

 _Another tap on the shoulder._

 _His creation, his non-biological son; Sensou, the Cyborg. Despite being 100% robot, "Cyborg" simply sounded cooler._

 _A glint on his wrist._

 _Pulling back his armor plating, he found a familiar gauntlet on his hand._

 _The Assimilator, a large otherworldly mech that outright defied the laws of conservation of matter, by being able to transform into almost anything, such as the metal glove that he wore. A triangular green eye looked up back at him._

 _Looking at the both his lover and his creation, he nodded, putting his hands on their shoulders._

 _A bright light, then the trio warped away._

* * *

 **[Moon Lord Lunaris has joined the Terrarian faction as a King!]**

 **[Lunatic Cultist Luken La Luna has joined the Terrarian faction as Lunaris' Mage!]**

 **[Lunar descendant Sensou has joined the Terraria faction as Lunaris' Warrior!]**

The trio making up the Lunar team rematerialized in some random empty lot.

"Huh. That's weird. This map of Japan doesn't show a town here." Lunaris grumbled, looking at a map of Japan he had always kept on him.

"I guess this Earth has an extra town." The red cyborg crossed his arms.

"It's been only 10 seconds and you're already saying that we're in an alternate universe that'd different than the one that visited Terraria thousands of years ago?"

"Yep."

…

…

…

"Huh, that's actually quite reasonable. I like it!"

"Hm~! If Moon Lord-sama likes it, then so do I!" Luken declares, crossing her arms as she leans over and winks at him, her face tinged pink as lewd thoughts began to fill her mind.

"...So...uh...what now?"

The three of them looked back at the empty lot upon which they stood.

"I have an idea..."

* * *

 **[The very next day...]**

Azazel, leader of the Fallen Angel faction, had seen some seriously shit back in the older times.

But honestly, seeing an entire building being built overnight in the lot next to his apartment?

Now that he had to check out.

He walked into the door, and immediately noticed the swath of magical presences that this entire place seemed to emit. Every floorboard, every window, even the food being displayed at the counter.

It was a cafe of all things, too.

Even more curiously was the fact that the cashier was pure magic. Not a single sign of him being a human save for his physical appearance.

"Hell yeah, first customer!"

"Uh...whuh...t-thanks?"

"Aye, it's no problem! The name's Sensou. No last name. Just Sensou. I'm just that cool."

* * *

Lunaris appeared to be asleep on his bed upstairs, while Luken snuggled up to him, hugging him tightly.

However, Lunaris was far from asleep.

Equations flowed through his mind like water in a river.

To a normal human, these equations would amount to nothing.

To him, however, it was magic. Literally.

He could sense the magic everywhere, not just the building whose bonds were held with mana.

Replace a variable here, adjust the mana converters to replicate a frequency...

Boom! He's tapped in.

He opened his eyes, allowing his cybernetics to get a reading on the magic in the air. From his studies of human cultures, there were supposedly many supernatural forces.

There they were. Spirits, Leylines, Mana, Arcane, chi, you name it.

He sat up in the bed, eliciting a few soft murmurs from his personal cultist.

He could see Azazel's outline through the floor. Slipping out of the bed, he left the room and walked down the stairs.

* * *

When Azazel heard the door open and felt a maelstrom of otherworldly forms of magic wash over him, he knew that someone had detected him.

He watched out of the corners of his eyes as the man menacingly walked over to him. His posture was that of a man who had seen some serious shit in his life.

He sat down.

The tension rose

Then he looked right at him, a smile on his face. The seriousness seemed to of have simply vanished.

"Sup. The name's Lunaris. Couldn't help but notice that you walked in, figured that I'd see who my first all-powerful first costumer is."

Charisma checks out.

"Alright, fine. You got me. Azazel of the Grigori, leader of the Fallen Angel faction."

"Grigori? You mean as in the watcher angels from the Book of Enoch sent by God to watch over the humans?"

"Before defecting to _mingle_ with the women? Who can blame 'em?"

They both laughed.

* * *

Chances are that you most likely know the backstory and everything about the great war between the three factions.

But here's the gist of it.

Long time ago three factions centered around Christianity got into a huge war.

There were a lot of fatalities and casualties and that jazz so right after these two Heavenl Dragons named Ddraig and Albion interfered, decided to have a truce and sealed the dragons away. Whilst it didn't mean an official peace, it kept them from killing each other. Most of the time. There was a rogue faction every now and then...

Azazel then noticed that Lunaris had seemed to be lost in thought.

"Hey buddy, you awake?"

"You know, it's nice that the fighting didn't continue up until this point."

"Hm...?"

Lunaris launched into lecture mode.

* * *

"Had the war kept going for too long, it would've spilled into the human world. When that happened, chaos would ensue, as it would reveal that these deities really are...well, real. Religious fanatics would take sides."

"Then, as the destruction tore across the planet, humans would develop technology to fight against you, no matter the cost. Even worse, many gods and deities depend on human belief in order to even exist. This drags them into the war for survival. "

"As humans grow desperate, they'd resort to more extreme methods, until it finally comes to the point where they launch the missiles."

Azazel's eyes widened.

"As you know, huge explosions are probably quite commonplace. However, nukes are another story altogether. Split a few atoms, and boom, you've got widespread destruction. Just look at Nagasaki and Hiroshima."

The Grigori leader knew all too well. He'd lost a few powerful members to those attacks.

"You see? Humans are fucking vicious. They're smart, but also really crazy. That's why they became the role models of Terrarians. Despite being traumatized war vets who could probably slay a god, we loved the humans. They gave us this glorious technology! Video games! Anime! So much more!"

Azazel could only stay silent, realizing how lucky he was pull his faction out of the war. He had grown to dislike the use of violence after losing many subordinates in several battles.

"Either that, or the humans die out and everyone gets pissed for a plethora of reasons." Lunaris finally added.

But now hearing what could've happened...

Oh HELL NO.

"Excuse me, I need to..erm...go outside for a moment."

"Go right ahead."

Outside of the cafe, Azazel walked into a nearby alleyway, and took a deep breath.

Then he screamed.

 ** _"GOD FUCKING DAMNIT, KOKABIEL!"_**

* * *

Kokabiel's plans were coming along smoothly.

Sure, there had been a small setback, he'd lost one of the three Excalibur pieces that he had obtained. But it didn't matter, just two alone would be powerful enough. If the Church was dumb enough to send more Excalibur wielders, then that would be amazing. What would've been even better was if he could get his hands on that sword spirit that called himself Excal...

 _"God fucking damnit Kokabiel!"_

Kokabiel, unaware of the potential consequences of starting the war anew, snickered.

* * *

Lunaris watched as Azazel walked back in, visibly a little miffed.

"Lemme guess...one of your associates is...?"

"Yep."

The ensuing silence was only broken by the sound of Sensou cooking pastries in the kitchen.

Until Azazel decided to change the subject.

"You...wouldn't happen to have a brother or sibling, would you?"

"Why yes- Do you know him?! Wears armor, green hair, four ankle-length ponytails, almost always accompanied by sword spirits, and smells like the ocean?!"

"Well, I haven't seen him for myself yet, but a few associates of mine had an encounter with him. Sent one to work for him after she helped him subdue some rogues. The big red one kind of adopted slash kidnapped one of the little ones."

"Big red one? Sounds like someone I know."

"Plus, this current wielder of the Boosted Gear was there too."

"The...Boosted Gear?"

The kitchen door opened.

"Well, speak of the devil."

* * *

Sensou had walked out into the back alley for a quick smoke break, before realizing that being a robot meant that he was unaffected by nicotine, so he tosses the cigarette away.

He didn't even know where he got them.

A gust of wind blows, a small pamphlet flies right into his face. He peels it off, looking at what's written on it.

 _"May your wishes come true."_

"Huh. Now that's a catchy slogan!" He mused to himself, unaware of a red magic circle and the pair of students standing in the middle of it; Asia Argento and Issei Hyoudou.

Until one of them, a blonde female, cleared her throat.

 _"-Ahem-_ Aau, we're here..to..umm.."

"Aye?!" Sensou flipped around to face her. He looked at the fading magical circle on the ground, then the pamphlet. "Oh. That's so cool! This actually summons people?!" A shit-eating grin forms on his face. "You know, I actually could use some help..."

* * *

So it was then while Asia Argento helped Sensou cook some delicious pastries, Issei Hyoudou was at the front counter.

"Yo. The name's Lunaris." The Moon Lord greeted, holding his hand out for the schoolboy to shake.

Which is what he did.

The former second king felt strange energies flowing through the boy's hand, both of which felt hauntingly familiar.

* * *

 _"Now, Cthulhu! Lunaris! Witness the powers that I have obtained!"_

 _"Omega Dragon Booster!"_

 ** _[Boost!]_**

 _"Where the hell did you get that?!"_

 _"Why, it's quite easy when you can travel between dimensions!"_

* * *

 _This kid...he gives off the magical signature of a Terrarian._

 _Not only that, but he has that boosting power that Tizona used against us._

 _Plus, he's also giving off a smaller energy frequency similar to that of the dragon lord's own. But...younger...?!_

* * *

"...Lunaris-senpai..?" Lunaris snapped out of his stupor when Issei called his name in concern.

"I...um...yes?"

"You kinda just spaced out there. You okay?"

"Oh, uh, yeah! T-This...I space out all the time!" He chuckled nervously, scratching the back of his head. Azazel and Issei both gave him a weird stare.

"So..eh...um...you're a devil, right?"

"Yeah! I'm the Pawn of Rias Gremory! I'm gonna one day become a High Class Devil and become the Harem King!"

"Hahaha!" The Moon Lord laughed. "That's the spirit! A truly magnificent dream!"

It was easy to say that the two of them got along right off the bat.

* * *

Several hours passed, and thus it was time for Issei and Asia to leave.

Sensou had decided to send her off with a box of freshly cooked pastries and a few Gold Coins.

As for Issei...

"Well, I know that you came here to accompany your friend, but I think you oughta get something too." Lunaris twirled his finger, materializing a small orange-colored orb. Wisps of flame twisted outward.

A Solar Fragment.

"It's not much, but i'm certain you could use it somehow!"

He gently drops it into Issei's outstretched hand. "Don't worry, it shouldn't burn you. Just...just don't leave it in your pocket for too long, alright?"

"Hai, Lunaris-senpai!"

"Please, call me Lunaris. I know that it's pretty cliche, but eh, i'm not the formal type!"

"Eh, alright!"

As the magical circle appeared beneath the two devils, both parties waved at each other until the former faded and teleported back to wherever they came from.

"I like that kid."

"You just gave the Boosted Gear's wielder a Solar Fragment from Terraria...?"

"Yeah! Ooh, you play Terraria too?! Awesome!"

"Ooh, you wanna come over to my place and have a LAN party?!"

"Hell yeah!"


End file.
